Radio control appararus, mobile communication method, mobile communication program, and mobile communication system

ABSTRACT

A radio control apparatus  2  has a transmission speed control section  23  and a memory section  22 . The transmission speed control section  23  calculates the transmission power of a data signal to be transmitted to a cell phone  41  based on the transmission power of a control signal to be transmitted to the cell phone  41  and an offset value to be applied to the transmission power of the control signal. The transmission speed control section  23  compares the transmission power of the data signal with an upper limit value stored in the memory section  22 , and performs control to decrease the transmission speed of the data signal when the transmission power of the data signal is greater than the upper limit value and to increase the transmission speed of the data signal when the transmission power of the data signal is less than or equal to the upper limit value.

TECHNICAL FIELD

The present inventtion relates to a radio control apparatus, a mobilecommunication method, a mobile communication program, and a mobilecommunication system.

BACKGROUND ART

Recently, with the development of radio communication technology, amobile communication system capable of high-speed and reliable datatransfer has been in use. Particularly, in a mobile packet communicationsystem, which uses the code division multiplexing scheme such as W-CDMA(Wideband—Code Division Multiple Access) and CDMA-2000, a technique inwhich communication channels are selectively used depending on thecharacteristics of the signal to be transmitted to a mobilecommunication terminal is adopted as a method of downward transmission.

For transmission of control signals, the A-DPCH (Associated-DedicatedPhysical CHannel) is used which is an individual downward channel (achannel dedicated to each terminal) suitable for high-speed transmissionpower control. To the contrary, for transmission of data signals, timedivision multiplexed communication is carried out using the DSCH(Downlink Shared CHannel), which is a common channel that allows radioresources to be used effectively among a plurality of mobilecommunication terminals. As described above, by appropriately switchingthe channels to be used depending on the property of the signals, aneffective signal transmission is carried out which makes use of theadvantages of both channels in a mutually complementary manner.

DISCLOSURE OF THE INVENTION

However, there are some problems in the above-described conventional artas follows. That is, in the mobile communication system using the codedivision multiplexing scheme, the same frequency band is used in all ofthe cells to provide services. Accordingly, the same frequency band maybe populated in a mixed manner with data communicated by a plurality ofservices including circuit switching services such as voicecommunication and ISDN (Integrated Services Digital Network) and packetswitching services. In order to handle such a communication mode, theupper limit value of transmission power is set up not only for each basestation but also for each of the services.

For example, suppose a case where the total transmission power which abase station can allocate to mobile communication terminals is 100. Amode may be considered where a cell containing a large number of usersin voice communication is allocated 60 of the transmission power to beused for the circuit switching services and 40 of the transmission powerto be used for the packet switching services. To the contrary, anothermode may also be considered where a cell containing a large number ofusers in data communication is allocated 20 of the transmission power tobe used for the circuit switching services and 80 of the transmissionpower to be used for the packet switching services.

As described above, depending on the cells visited by mobilecommunication terminals and the usage situation of services, the upperlimit value of the transmission power varies with time, and theavailable transmission power is limited. On the other hand, in the DSCH,although the transmission speed can be changed at regular intervals oftime (for example, 10 ms) in accordance with standard regulations, thetechnique thereof has not been established. Therefore, a fixedtransmission speed (for example, 384 kbps) is set up at the start ofdata transmission.

Accordingly, data may be transmitted and received at a transmissionspeed unsuitable for the transmission power. To be more precise, whenthe transmission speed is higher than the transmission speed suitablefor the transmission power, the DSCH cannot be supplied with sufficienttransmission power, resulting in a reduction of communication quality ofthe data. To the contrary, when the transmission speed is lower than thetransmission speed suitable for the transmission power, the data will becommunicated at a lower transmission speed although the data could betransmitted at a higher speed.

The present invention has been proposed in view of the above-describedproblems. An object of the present invention is to provide a radiocontrol apparatus, a mobile communication method, a mobile communicationprogram and a mobile communication system, which controls thetransmission speed in accordance with the transmission power, therebyachieving a high-speed data communication while suppressing the decreaseof communication quality.

The present invention provides a radio control apparatus for controllingdownward packet communication between a mobile communication terminaland a base station by using a channel specific to each of a plurality ofmobile communication terminals to cause a control signal to betransmitted and using a channel common to the plurality of mobilecommunication terminals in a time-division manner to cause a data signalto be transmitted, comprising: calculation means for calculating, basedon a transmission power of the control signal to be transmitted to aparticular mobile communication terminal of said plurality of mobilecommunication terminals and an offset value to be applied to thetransmission power of the control signal, the transmission power of thedata signal to be transmitted to said particular mobile communicationterminal; storage means for storing an upper limit value of thetransmission power of said data signal; comparison means for comparingthe transmission power of the data signal calculated by said calculationmeans with said upper limit value stored in said storage means; andcontrol means for performing control, as a result of comparison by saidcomparison means, to decrease the transmission speed of said data signalwhen the transmission power of said data signal is greater than saidupper limit value, and to increase the transmission speed of said datasignal when the transmission power of said data signal is less than saidupper limit value.

The present invention provides a mobile communication method performedby a radio control apparatus for controlling downward packetcommunication between a mobile communication terminal and a base stationby using a channel specific to each of a plurality of mobilecommunication terminals to cause a control signal to be transmitted andusing a channel common to the plurality of mobile communicationterminals in a time-division manner to cause a data signal to betransmitted, comprising: a calculating step of calculating, by saidradio control apparatus, based on a transmission power of the controlsignal to be transmitted to a particular mobile communication terminalof said plurality of mobile communication terminals and an offset valueto be applied to the transmission power of the control signal, thetransmission power of the data signal to be transmitted to saidparticular mobile communication terminal; a storing step of storing, bysaid radio control apparatus, an upper limit value of the transmissionpower of said data signal in storage means; a comparing step ofcomparing, by said radio control apparatus, the transmission power ofthe data signal calculated in said calculating step with said upperlimit value stored in said storage means; and a controlling step ofperforming control, by said radio control apparatus, as a result ofcomparison in said comparing step, to decrease the transmission speed ofsaid data signal when the transmission power of said data signal isgreater than said upper limit value, and to increase the transmissionspeed of said data signal when the transmission power of said datasignal is less than said upper limit value.

The present invention provides a mobile communication program forcontrolling downward packet communication between a mobile communicationterminal and a base station by using a channel specific to each of aplurality of mobile communication terminals to cause a control signal tobe transmitted and using a channel common to the plurality of mobilecommunication terminals in a time-division manner to cause a data signalto be transmitted, instructing a computer to perform: a calculatingoperation for calculating, based on a transmission power of the controlsignal to be transmitted to a particular mobile communication terminalof said plurality of mobile communication terminals and an offset valueto be applied to the transmission power of the control signal, thetransmission power of the data signal to be transmitted to saidparticular mobile communication terminal; a storing operation forstoring an upper limit value of the transmission power of said datasignal in storage means; a comparing operation for comparing thetransmission power of the data signal calculated by said calculatingoperation with said upper limit value stored in said storage means; anda controlling operation for performing control, as a result ofcomparison by said comparing operation, to decrease the transmissionspeed of said data signal when the transmission power of said datasignal is greater than said upper limit value, and to increase thetransmission speed of said data signal when the transmission power ofsaid data signal is less than said upper limit value.

According to these inventions, depending on the transmission power ofthe control signal transmitted on a channel specific to each of aplurality of mobile communication terminals, the transmission speed ofthe data signal transmitted on a channel common to the plurality ofmobile communication terminals in a time-division manner is dynamicallycontrolled. That is, when the transmission power of the data signal isgreater than an upper limit value, a control for decreasing thetransmission speed of the data signal is carried out. Owing to thiscontrol, since a sufficient transmission power suitable for thetransmission speed can be supplied to the DSCH, the communicationquality of the data is increased. This enables to reduce theretransmission rate due to transmission error and the interference withother radio connections, resulting in an increase of transmissioncapacity per unit time (throughput) . On the other hand, when thetransmission power of the data signal is less than or equal to the upperlimit value, a control for increasing the transmission speed of the datasignal is carried out. Owing to this control, it is possible to increasethe speed of the data transmission. As a result, it is possible toachieve a high-speed data communication while suppressing the decreaseof communication quality.

Preferably, the calculation means of the radio control apparatuscalculates the transmission power of said data signal based on anaverage value of the transmission powers of said control signal over apredetermined period of time and an average value of said offset valuesover a predetermined period of time.

Preferably, the calculating step in the mobile communication methodcomprises calculating the transmission power of said data signal basedon an average value of the transmission powers of said control signalover a predetermined period of time and an average value of said offsetvalues over a predetermined period of time.

Preferably, the calculating operation performed by the mobilecommunication program comprises calculating the transmission power ofsaid data signal based on an average value of the transmission powers ofsaid control signal over a predetermined period of time and an averagevalue of said offset values over a predetermined period of time.

According to these inventions, the transmission power of the data signalis calculated based on an average value of the transmission powers ofthe control signal and an average value of the offset values. Thisenables to control the transmission speed of the data signal based on aprecise transmission power from which influence of fluctuation of thetransmission power and/or offset value accompanying accidental changesin the communication environment is maximally eliminated.

Also preferably, the radio control apparatus further comprises low-speedtransmission power calculation means for calculating the transmissionpower of the data signal in the case of having decreased thetransmission speed of said data signal when the transmission power ofsaid data signal is greater than said upper limit value as a result ofcomparison by said comparison means, wherein said control means performscontrol to decrease the transmission speed of said data signal until thetransmission power of the data signal calculated by said low-speedtransmission power calculation means becomes less than or equal to saidupper limit value.

Also preferably, the mobile communication method further comprises alow-speed transmission power calculating step of calculating, by saidradio control apparatus, the transmission power of the data signal inthe case of having decreased the transmission speed of said data signalwhen the transmission power of said data signal is greater than saidupper limit value as a result of comparison in said comparing step,wherein said controlling step comprises performing control to decreasethe transmission speed of said data signal until the transmission powerof the data signal calculated in said low-speed transmission powercalculating step becomes less than or equal to said upper limit value.

Also preferably, the mobile communication program further instructs thecomputer to perform a low-speed transmission power calculating operationfor calculating the transmission power of the data signal in the case ofhaving decreased the transmission speed of said data signal when thetransmission power of said data signal is greater than said upper limitvalue as a result of comparison in said comparing operation, whereinsaid controlling operation instructs the computer to perform anoperation to decrease the transmission speed of said data signal untilthe transmission power of the data signal calculated by said low-speedtransmission power calculating operation becomes less than or equal tosaid upper limit value.

According to these inventions, the transmission speed of the data signalis controlled so that the transmission power of the data signal becomesless than or equal to the upper limit value. And at a point of time whenthe transmission power of the data signal becomes less than or equal tothe upper limit value, the control for decreasing the transmission speedof the data signal is terminated. Accordingly, when the transmissionspeed of the data signal is decreased to maintain the communicationquality, the transmission speed is not decreased more than necessary. Asa result, data transmission can be achieved while maintaining thecommunication quality as well as suppressing the decrease oftransmission speed.

Still preferably, the radio control apparatus further compriseshigh-speed transmission power calculation means for calculating thetransmission power of the data signal in the case of having increasedthe transmission speed of said data signal when the transmission powerof said data signal is less than said upper limit value as a result ofcomparison by said comparison means, wherein said control means performscontrol to increase the transmission speed of said data signal until thetransmission power of the data signal calculated by said high-speedtransmission power calculation means reaches a maximum value within arange in which said upper limit value is not exceeded.

Still preferably, the mobile communication method further comprises ahigh-speed transmission power calculating step of calculating, by saidradio control apparatus, the transmission power of the data signal inthe case of having increased the transmission speed of said data signalwhen the transmission power of said data signal is less than said upperlimit value as a result of comparison in said comparing step, whereinsaid controlling step comprises performing control to increase thetransmission speed of said data signal until the transmission power ofthe data signal calculated in said high-speed transmission powercalculating step reaches a maximum value within a range in which saidupper limit value is not exceeded.

Also preferably, the mobile communication program further instructs thecomputer to perform a high-speed transmission power calculatingoperation for calculating the transmission power of the data signal inthe case of having increased the transmission speed of said data signalwhen the transmission power of said data signal is less than said upperlimit value as a result of comparison in said comparing operation,wherein said controlling operation instructs the computer to perform anoperation to increase the transmission speed of said data signal untilthe transmission power of the data signal calculated by said high-speedtransmission power calculating operation reaches a maximum value withina range in which said upper limit value is not exceeded.

According to these inventions, the transmission speed of the data signalis controlled so that its maximum value is obtained within an allowablerange of transmission speed of the data signal. Accordingly, it ispossible to carry out the data transmission at a highest transmissionspeed within a range in which the communication quality can bemaintained. As a result, the throughput can be increased more easily.

Also, when a computer-readable recording medium on which theabove-described mobile communication program is stored is sold anddistributed as a stand-alone or attached product, it is possible topractice the mobile communication technique according to the presentinvention widely and inexpensively. Furthermore, it may be operated as amobile communication system comprised of the above-described radiocontrol apparatus and a base station, where the base station iscontrolled by the control means of the radio control apparatus andtransmits data signals to mobile communication terminals at atransmission speed of the data signals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram showing an example of an entireconfiguration of a mobile communication system according to the presentinvention;

FIG. 2 is a schematic diagram for illustrating a functionalconfiguration of the mobile communication system;

FIG. 3A is a diagram showing an example of data storage within atransmission power storage section, FIG. 3B is a diagram showing anexample of data storage within an allowable maximum transmission powerstorage section, and FIG. 3C is a diagram showing an example of datastorage within an initial offset value storage section;

FIG. 4 is a flowchart for illustrating a DSCH transmission speed controloperation;

FIG. 5 is a flowchart for illustrating a DSCH transmission speeddecreasing operation;

FIG. 6 is a flowchart for illustrating a DSCH transmission speedincreasing operation; and

FIG. 7 is a diagram showing a configuration of a recording medium onwhich a program according to the present invention is stored.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the attached drawings, an embodiment of the presentinvention will now be described in detail.

First, the configuration will be described. FIG. 1 is a schematicdiagram showing an example of the entire configuration of a mobilecommunication system 100 in the present embodiment. As shown in FIG. 1,the mobile communication system 100 comprises a switch 1 that functionsas a relay point for public base stations, a radio control apparatus 2that integrally controls packet communications between public basestations and cell phones, public base stations 31, 32, 33, . . . thatperform radio communication directly with cell phones within apredetermined communication area, and cell phones (corresponding tomobile communication terminals) 41, 42, 43, . . . that are carried andused by users. The above elements form a hierarchy being connected toeach other to allow two-way communication.

As the premises for the description, assuming that, in a downward radioconnection (hereinafter referred to as “downlink”) from a public basestation toward a cell phone, a plurality of signals havingcharacteristics different from each other are transmitted, the mobilecommunication system 100 uses two kinds of channels. That is, when acontrol signal requiring relatively small transmission power istransmitted, a downward channel (hereinafter referred to as “A-DPCH”)individually allocated to each cell phone is used. To the contrary, whena data signal requiring large transmission power and high-speedperformance is transmitted, a channel common to a plurality of cellphones (hereinafter referred to as “DSCH”) is used in a time-divisionmanner.

Referring to FIG. 2, the internal configuration of the radio controlapparatus 2 will now be described in detail. FIG. 2 is a block diagramshowing a functional configuration of the radio control apparatus 2. Asshown in FIG. 2, the radio control apparatus 2 comprises a calladmission control section 21, a memory section 22 (corresponding tostorage means), a transmission speed control section 23 (correspondingto calculation means, comparison means, control means, low-speedtransmission power calculation means, and high-speed transmission powercalculation means), a queue processing section 24, and an A-DPCHtransmission power monitoring section 25, where the sections areconnected to each other via a bus. Arrows in the figure indicate thetransmission direction of signals. Dotted lines indicate that thesignals are control signals, and solid lines indicate data signals. Eachof the components will be described in detail below.

The call admission control section 21 monitors call origination requestsand disconnection requests from any one of the cell phones 41, 42, 43, .. . and determines whether the request should be admitted. Whenadmission is permitted, a user data buffer is reserved for the admittedcell phone, and a wired connection with the switch 1 is set up. At thesame time, the call admission control section 21 forms a data storageregion for the admitted cell phone in a transmission power storagesection 221 of the memory section 22 described later, and initializesthe same.

The memory section 22 comprises a transmission power storage section221, an allowable maximum transmission power storage section 222, and aninitial offset value storage section 223. Referring to FIGS. 3A to 3C,an example of the data storage within the memory section 22 will bedescribed in detail.

As shown in FIG. 3A, the transmission power storage section 221 containsa terminal ID storage region 221 a, a transmission speed storage region221 b, a transmission power storage region 221 c, and an offset valuestorage region 221 h. The terminal ID storage region 221 a stores anumerical data (for example, “1”, “2”, . . . “N”) as “terminal ID”,which data is uniquely assigned to each of the cell phones in order toidentify them. The transmission speed storage region 221 b stores anumerical value data (for example, “256”, “128”, . . . , “64”) as“transmission speed”, which data indicates the transmission speed (inkbps) of data at time t when the DSCH is used in such a manner that thevalues can be sequentially updated with latest values.

The transmission power storage region 221 c is a data storage regionthat stores the time-varying transmission powers (in dBm) of the A-DPCHin a historical order. In order to enable such a storage mode, thetransmission power storage region 221 c contains a time (t−k) datastorage region 221 d, a time (t−k+1) data storage region 221 e, . . . ,a time t data storage region 221 f, and an average value storage region221 g.

To be more precise, the time (t−k) data storage region 221 d is a regionin which the transmission power (for example, “23”, “25”, . . . , “24”)of the A-DPCH obtained at a point of time earlier than the current timet by a period of time k is recorded. The value k is, for example,200-300 ms. Likewise, the time (t−k+1) data storage region 221 e is aregion in which the transmission power (for example, “26”, “23”, . . . ,“23”) of the A-DPCH obtained at a point of time earlier than the currenttime t by a period of time k−1 is recorded. Further, the time t datastorage region 221 f is a region in which the transmission power (forexample, “23”, “27”, . . . , “25”) of the A-DPCH obtained at time t(current) is recorded.

The average value storage region 221 g is a region in which the averagevalue (for example, “24”, “25”, . . . , “23”) of the transmission powersof the A-DPCH in a period of time k from time (t−k) to time t isrecorded. Practically, the average value storage region 221 g stores theaverage value of all data of the transmission powers of the A-DPCHcorresponding to each terminal ID within the period of time from time(t−k) to time t. However, for simplicity, it is assumed that the averagevalue of three data is stored.

Further, the offset value storage region 221 h is a data storage regionthat stores time-varying offset values (in dB) in a historical order.Here, the offset value refers to a value that may be applied (added,multiplied or otherwise) to the transmission power of the A-DPCH inorder to determine the transmission power of the DSCH. The offset valuevaries with time based on the reception error rate or the like of themobile communication terminal. Generally, the offset value gets greaterwhen the transmission speed of the DSCH is higher, while it gets smallerwhen the transmission speed of the DSCH is lower. Further, the offsetvalue gets smaller when the radio connection condition is better, whileit gets greater when the radio connection condition is worse.

In order to enable the above-described storage mode, the offset valuestorage region 221 h contains a time (t−k) data storage region 221 i, atime (t−k+1) data storage region 221 j, . . . , a time t data storageregion 221 k, and an average value storage region 221 l.

To be more precise, the time (t−k) data storage region 221 i is a regionin which the offset value (for example, “11.0”, “9.7”, . . . , “4.5”)obtained at a point of time earlier than the current time t by a periodof time k is recorded. Likewise, the time (t−k+1) data storage region221 j is a region in which the offset value (for example, “13.3”,“11.5”, . . . , “4.3”) obtained at a point of time earlier than thecurrent time t by a period of time k−1 is recorded. Further, the time tdata storage region 221 k is a region in which the offset value (forexample, “13.2”, “9.4”, . . . , “7.1”) obtained at time t (current) isrecorded.

The average value storage region 221 l is a region in which the averagevalue (for example, “12.5”, “10.2”, . . . , “5.3”) of the offset valuesin a period of time k from time (t−k) to time t is recorded.Practically, the average value storage region 221 l stores the averagevalue of all data of the offset values corresponding to each terminal IDwithin the period of time from time (t−k) to time t. However, forsimplicity, it is assumed that the average value of three data isstored.

As shown in FIG. 3B, the allowable maximum transmission power storagesection 222 stores a numerical value data (for example, “36.0”) as“allowable maximum transmission power”, which data indicates the upperlimit value of the transmission power (in dBm) of the DSCH. For theallowable maximum transmission power, a value common to the public basestations 31, 32, 33, . . . may be used, or the value may be separatelyset for each public base station depending on the communicationenvironment or the like.

The initial offset value storage section 223 stores an initial value ofthe offset value in association with the transmission speed of the DSCH.As shown in FIG. 3C, the initial offset value storage section 223contains a transmission speed storage region 223 a and an initial offsetvalue storage region 223 b. The transmission speed storage region 223 astores a numerical value data (for example, “384”, “256”, “128”, “64”)as “transmission speed”, which data indicates the transmission speed (inkbps) of the data using the DSCH in a stepwise manner. The offset valuestorage region 223 b stores a numerical value data (for example, “16.0”,“13.0”, “10.0”, “7.0”) as “initial offset value”, which data indicatesthe offset value (in dB) applied to the transmission power of the A-DPCHwhen the communication is started or when the transmission speed ischanged.

Referring to FIG. 2 again, the transmission speed control section 23calculates the transmission power of the DSCH based on the transmissionpower of the A-DPCH and the offset value, determines the transmissionspeed of the DSCH in accordance with the calculated transmission powerof the DSCH, and then instructs the public base stations 31, 32, 33through the queue processing section 24 described later to transmit datasignals at the determined transmission speed. Also, the transmissionspeed control section 23 calculates an average value of the transmissionpowers of the A-DPCH and an average value of the offset values based onthe data stored in the transmission power storage section 221.

The queue processing section 24 obtains the transmission speed of theDSCH from the transmission speed storage region 221 b, and extractstransmission data having a volume of data (for example, number ofpackets) corresponding to the obtained transmission speed from the userdata buffer. The queue processing section 24 transfers the transmissiondata to a DSCH transmission section 312 of the public base station 31described later and instructs it to transmit the data to the cell phone41. Also, the queue processing section 24 notifies the public basestation 31 of the offset value to be applied to the transmission powerof the A-DPCH.

The A-DPCH transmission power monitoring section 25 periodicallymonitors the transmission power of the A-DPCH between the public basestation 31 described later and the cell phones 41, 42, 43, . . . , andthen records the monitored results in the transmission power storageregion 221 c corresponding to the terminal ID of each cell phone formedin the transmission power storage section 221. Since the numerical valuedata indicating the transmission power of the A-DPCH is updatedsequentially at the same time as the monitoring, the latest transmissionpower for each cell phone is always recorded in the transmission powerstorage region 221 c.

The public base station 31 comprises at least an A-DPCH transmissionsection 311 that performs signal transmission using the A-DPCH as acommunication channel, a DSCH transmission section 312 that performssignal transmission using the DSCH in a time-division manner, and a DPCHreception section 313 that performs signal reception using the DPCH,which is an upward channel.

The A-DPCH transmission section 311 transmits a control signal whichpreviously notifies the cell phone 41 that a data signal is transmittedwith the A-DPCH. Since the transmission of the control signal is carriedout prior to the data transfer, the cell phone 41 can recognize the factbefore receiving the data signal. This enables the public base station31 to change arbitrarily the cell phone to which the data istransmitted. As for the transmission speed of the control signal, afixed speed specified by a communication carrier or relevantstandardization body is used.

Only when the A-DPCH transmission section 311 has transmitted thecontrol signal, the DSCH transmission section 312 establishes a DSCHwith the cell phone, and transmits the data signal using the DSCH. Thetransmission speed of the data signal is variably determined atpredetermined intervals of time (for example, 10 ms) specified by therelevant standard. As will be described in detail later, the DSCHtransmission section 312 applies the offset value specified by the queueprocessing section 24 to the transmission power of the A-DPCH todetermine the transmission power of the DSCH.

The DPCH reception section 313 receives a control command for thetransmission power of the DPCH from the cell phone 41. This controlcommand allows the transmission power of the A-DPCH between the publicbase station 31 and the cell phone 41 to be optimally controlled.

Since the cell phone 41 is a well-known cell phone, the detaileddescription thereof will be omitted. The cell phone 41 comprises atleast an A-DPCH reception section 411, a DSCH reception section 412 anda DPCH transmission section 413. The A-DPCH reception section 411receives a control signal from the A-DPCH transmission section 311 ofthe public base station 31. If the DSCH reception section 412 previouslyreceives a notice of transmission of a data signal via the controlsignal, the DSCH reception section 412 starts to receive the data signalfrom the DSCH transmission section 312 of the public base station 31.The DPCH transmission section 413 transmits a control command foroptimally controlling the transmission power of the A-DPCH to the publicbase station 31 using the A-DPCH as a communication channel.

The configuration of each terminal device constituting the mobilecommunication system 100 according to the present invention has beendescribed. Since the essential configuration of the public base stations32, 33, . . . , and the cell phones 42, 43, . . . shown in FIG. 1 is thesame as the configuration of the public base station 31 and the cellphone 41 described in detail, respectively, the illustration and thedetailed description thereof will be omitted. That is, each of thepublic base stations 32 and 33 is provided with an A-DPCH transmissionsection 321, 331, a DSCH transmission section 322, 332 and a DPCHreception section 323, 333. Further, each of the cell phones 42 and 43is provided with an A-DPCH reception section 421, 431, a DSCH receptionsection 422, 432 and a DPCH transmission section 423, 433.

Next, referring to FIGS. 4 to 6, the operations in the presentembodiment will be described. Particular attention will now be paid tothe case where a call origination request is made from the cell phone 41(having terminal ID 1) visiting a communication area of the public basestation 31 for describing illustratively the transmission speed controloperations between the public base station 31 and the cell phone 41.However, the present invention is not limited to the transmission speedcontrol technique between these devices.

FIG. 4 is a flowchart for illustrating the DSCH transmission speedcontrol operation carried out by the radio control apparatus 2. First,in S1, the transmission speed control section 23 obtains an averagevalue A of the transmission powers of the A-DPCH corresponding to theterminal ID “1” from the average value storage region 221 g. Thetransmission speed control section 23 obtains an average value O of theoffset values corresponding to the terminal ID “1” from the averagevalue storage region 2211. The transmission speed control section 23calculates a transmission power P of the DSCH from the obtained averagevalue A of the transmission powers of the A-DPCH and the average value Oof the offset values. For example, in the case of the transmission speedcontrol operation between the cell phone 41 and the public base station31, the average value A of the transmission powers of the A-DPCH is 24dBm, and the average value O of the offset values is 12.5 dB.Accordingly, the transmission power of the DSCH is calculated as 36.5dBm, which is the sum of them.

In this embodiment, since both of the average value A of thetransmission powers of the A-DPCH and the average value O of the offsetvalues are expressed in logarithm, the transmission power of the DSCHcan be calculated by addition operation. In the case where both of theaverage value A of the transmission powers of the A-DPCH and the averagevalue O of the offset values are actual numbers, the transmission powerof the DSCH may be calculated by multiplication operation.

The reason why the transmission power of the DSCH is calculated byapplying the offset value to the transmission power of the A-DPCH asdescribed above is as follows. That is, the transmission power of theA-DPCH is always optimally controlled based on the control commandtransmitted from the cell phone 41 to the public base station 31 asdescribed above. On the other hand, when the cell phone 41 receives asignal from the public base station 31, the A-DPCH and the DSCH are usedat the same time using different spread codes. Accordingly, in thecommunication using the code division multiplexing scheme, the radioconnection conditions of the A-DPCH and the DSCH can be regarded as thesame. Therefore, the transmission power of the DSCH is adapted to bedetermined in conjunction with the transmission power of the A-DPCH byapplying a given value (offset value) to the transmission power of theA-DPCH.

In S2, the transmission speed control section 23 obtains an allowablemaximum transmission power T from the allowable maximum transmissionpower storage section 222. Then, the transmission speed control section23 compares (S3) the transmission power P of the DSCH calculated in S1with the allowable maximum transmission power T obtained in S2.

As a result of the comparison operation, when the transmission power Pof the DSCH is greater than the allowable maximum transmission power T(i.e., in the case of P>T), the transmission speed control section 23determines that the current transmission power of the DSCH is too large,and starts an operation for decreasing the transmission speed of theDSCH (S4). To the contrary, in S3, when the transmission power P of theDSCH is less than or equal to the allowable maximum transmission powerT, (i.e., in the case of P≦T), the transmission speed control section 23determines that the current transmission power of the DSCH is less thanor equal to the upper limit value and the transmission speed of the DSCHmay be increased, and starts the DSCH transmission speed increasingoperation (S5). Following the completion of the operation S4 or S5, thesequence of the DSCH transmission speed control operations isterminated.

Referring to FIG. 5, the DSCH transmission speed decreasing operationshown in S4 will now be described. First, in S41, the transmission speedcontrol section 23 obtains a transmission speed R of the DSCH at thecurrent time (time t) from the transmission speed storage region 221 b.

Then, the transmission speed control section 23 obtains an initialoffset value Oi in the case of having decreased the transmission speed Rof the DSCH obtained in S41 by one step, from the initial offset valuestorage region 223 b (S42). For example, in the case of the transmissionspeed control operation between the cell phone 41 and the public basestation 31, the transmission speed of the DSCH at time t is 256 kbps.Accordingly, the transmission speed control section 23 obtains aninitial offset value of 10 dB corresponding to the transmission speed128 kbps, which is lower than 256 kbps by one step.

Next, in S43, the transmission speed control section 23 obtains anaverage value A of the transmission powers of the A-DPCH correspondingto the terminal ID “1” of the cell phone 41 from the average valuestorage region 221 g. The transmission speed control section 23calculates a transmission power P′ of the DSCH based on the obtainedaverage value A of the transmission powers of the A-DPCH and the initialoffset value Oi obtained in S42. For example, in the case of thetransmission speed control operation between the cell phone 41 and thepublic base station 31, since the average value A of the transmissionpowers of the A-DPCH is 24 dBm and the initial offset value obtained inS42 is 10 dB, the transmission power of the DSCH is calculated as 34dBm.

In S44, the transmission speed control section 23 compares thetransmission power P′ of the DSCH calculated in S43 and the allowablemaximum transmission power T obtained in S2 in FIG. 4. As a result ofthe comparison operation, when the transmission power P′ of the DSCH isgreater than the allowable maximum transmission power T (i.e., in thecase of P′>T), the transmission speed control section 23 determines thatthe transmission power of the DSCH will still have too large a value,and sets the transmission speed of the DSCH to a value decreased by onemore step (S45).

After completing S45, in order to confirm whether the transmission speedof the DSCH has to be further decreased, the transmission speed controlsection 23 returns to S41 and carries out the operations from S41. InS41, the transmission speed of the DSCH set in S45 is obtained as thecurrent transmission speed R of the DSCH. The sequence of operationsS41-S45 are carried out repeatedly until the comparison result in S44meets P′≦T.

On the other hand, in S44, when the transmission power P′ of the DSCH isless than or equal to the allowable maximum transmission power T (i.e.,in the case of P′≦T), the transmission speed control section 23determines that the transmission power of the DSCH is within anallowable range, and decreases the transmission speed of the DSCH to thecurrently set transmission speed of the DSCH (S46).

The decreased transmission speed of the DSCH is updated and stored inthe transmission speed storage region 221 b corresponding to theterminal ID “1”. Further, the initial offset value corresponding to thedecreased transmission speed of the DSCH is updated and stored in thetime t data storage region 221 k as the current offset value. Aftercompleting S46, the sequence of DSCH transmission speed controloperations is terminated.

Next, referring to FIG. 6, the DSCH transmission speed increasingoperation shown in S5 will be described in detail. First, in S51, thetransmission speed control section 23 obtains a transmission speed R ofthe DSCH at the current time (time t) from the transmission speedstorage region 221 b.

Then, the transmission speed control section 23 obtains an initialoffset value Oi in the case of having increased the transmission speed Rof the DSCH obtained in S51 by one step, from the initial offset valuestorage region 223 b (S52). For example, in the case of the transmissionspeed control operation between the cell phone 41 and the public basestation 31, the transmission speed of the DSCH at time t is 256 kbps.Accordingly, the transmission speed control section 23 obtains 16 dB asan initial offset value corresponding to the transmission speed 384kbps, which is higher than 256 kbps by one step.

Next, in S53, the transmission speed control section 23 obtains anaverage value A of the transmission powers of the A-DPCH correspondingto the terminal ID “1” of the cell phone 41 from the average valuestorage region 221 g. The transmission speed control section 23calculates the transmission power P″ of the DSCH based on the obtainedaverage value A of the transmission powers of the A-DPCH and the initialoffset value Oi obtained in S52. For example, in the case of thetransmission speed control operation between the cell phone 41 and thepublic base station 31, since the average value A of the transmissionpowers of the A-DPCH is 24 dBm, and the initial offset value obtained inS52 is 16 dB, the transmission power of the DSCH calculated as 40 dBm.

In S54, the transmission speed control section 23 compares thetransmission power P″ of the DSCH calculated in S53 with the allowablemaximum transmission power T obtained in S2 in FIG. 4. As a result ofthe comparison operation, when the transmission power P″ of the DSCH isless than or equal to the allowable maximum transmission power T (i.e.,in the case of P″≦T), the transmission speed control section 23determines that the transmission power falls within the allowable rangeeven if the transmission speed of the DSCH is increased by one step, andsets the transmission speed of the DSCH to a value increased by one step(S55).

After completing S55, in order to confirm whether the transmission speedof the DSCH can be further increased, the transmission speed controlsection 23 returns to S51 and carries out the operations from S51. InS51, the transmission speed of the DSCH changed in S55 is obtained asthe current transmission speed R of the DSCH. The sequence of operationsS51-S55 are carried out repeatedly until the comparison result in S54meets P″>T.

On the other hand, in S54, when the transmission power P″ of the DSCH isgreater than the allowable maximum transmission power T (i.e., in thecase of P″>T), the transmission speed control section 23 determines thatthe transmission power of the DSCH exceeds the allowable range, andproceeds to the operation of S56. In S56, the transmission speed controlsection 23 increases the transmission speed of the DSCH up to thetransmission speed one step lower than the currently set transmissionspeed of the DSCH (S56).

The reason why the transmission speed of the DSCH is increased up to astep which is one step lower than the current setting is as follows.That is, the transmission speed of the DSCH set up at a point of timewhen the operation of S56 is carried out is a value immediately afterthe allowable maximum transmission power T is exceeded as a result thatthe transmission speed of the DSCH has been increased. Accordingly, thevalue immediately before the allowable maximum transmission power T isexceeded gives a value less than or equal to the allowable maximumtransmission power T and a maximum transmission speed within theallowable range.

The increased transmission speed of the DSCH is updated and stored inthe transmission speed storage region 221 b corresponding to theterminal ID “1”. Further, the initial offset value corresponding to theincreased transmission speed of the DSCH is updated and stored in thetime t data storage region 221 k as the current offset value. Aftercompleting S56, the sequence of DSCH transmission speed controloperations is terminated.

As described above, according to the mobile communication system 100 inthe present embodiment, the radio control apparatus 2 comprises thetransmission speed control section 23 and the memory section 22. Thetransmission speed control section 23 calculates the transmission powerof the data signal to be transmitted to the cell phone 41 based on thetransmission power of the control signal to be transmitted to the cellphone 41 and the offset value to be applied to the transmission power ofthe control signal. The transmission speed control section 23 comparesthe transmission power of the data signal with the upper limit valuestored in the memory section 22, and when the transmission power of thedata signal is greater than the upper limit value, performs control fordecreasing the transmission speed of the data signal. This controlallows the radio control apparatus 2 to supply sufficient transmissionpower suitable for the transmission speed to the DSCH. Accordingly, thecommunication quality of the data is increased. This enables to reducethe retransmission rate due to transmission error and the interferenceaffecting other radio connections. As a result, the volume of datatransmitted per unit time can be increased. On the other hand, when thetransmission power of the data signal is less than or equal to the upperlimit value, the radio control apparatus 2 performs control forincreasing the transmission speed of the data signal. This controlallows the radio control apparatus 2 to achieve a higher speed of datatransmission. As a result, it is possible to achieve a high-speed datacommunication while suppressing the decrease of communication quality.

Preferably, the transmission speed control section 23 calculates thetransmission power of the data signal based on the average value of thetransmission powers of the control signal over a predetermined period oftime and the average value of the offset values over a predeterminedperiod of time. This allows the radio control apparatus 2 to control thetransmission speed of the data signal based on a highly precisetransmission power from which influences of fluctuation in thetransmission power or the offset value accompanying any sudden change inthe communication environment are maximally removed.

More preferably, when the transmission power of the data signal isgreater than the upper limit value, the transmission speed controlsection 23 calculates the transmission power of the data signal in thecase of having decreased the transmission speed of the data signal. Thetransmission speed control section 23 performs control for decreasingthe transmission speed of the data signal until the calculatedtransmission power of the data signal becomes less than or equal to theupper limit value. At a point of time when the transmission power of thedata signal becomes less than or equal to the upper limit value, thecontrol for decreasing the transmission speed of the data signal isterminated. Accordingly, if the transmission speed of the data signal isdecreased in order to maintain the communication quality, thetransmission speed is not decreased more than necessary. As a result, itis possible to carry out data transmission with a suppressed decrease oftransmission speed while maintaining the communication quality.

More preferably, when the transmission power of the data signal is lessthan or equal to the upper limit value, the transmission speed controlsection 23 calculates the transmission power of the data signal in thecase of having increased the transmission speed of the data signal. Thetransmission speed control section 23 performs control for increasingthe transmission speed of the data signal until the calculatedtransmission power of the data signal reaches the maximum value within arange in which the upper limit value is not exceeded. Accordingly, it ispossible to perform the data transmission at the highest transmissionspeed within a range such that the communication quality can bemaintained. As a result, the throughput can be increased more easily.

The aspect described in the present embodiment is a preferred example ofthe mobile communication system according to the present invention, andis not limited thereto. For example, in the present embodiment, from theviewpoint of reliability of the calculation result, the transmissionpower of the DSCH is calculated based on the average value of thetransmission powers of the A-DPCH and the average value of the offsetvalues. However, at least one of the transmission power of the A-DPCHand the offset value may be an instantaneous value. This enables toeliminate the operations of calculating the average value by thetransmission speed control section 23, resulting in a reduction ofprocessing load. Also, the data region for storing the previouslyobtained transmission powers and offset values can be saved.

In the present embodiment, although the description has been madeassuming a cell phone as a mobile communication terminal, anyinformation equipment having a radio communication function, such as PDA(Personal Digital Assistance), may be used.

Further, in the above embodiment, an example has been described in whichthe radio control apparatus 2 controls the transmission speed of thedata signal with the transmission speed control section 23 . However,the public base station 31 may be adapted to control the transmissionspeed of the data signal. In this case, the public base station 31further has the above-described function of the memory section, thefunction of the transmission speed control section, part of the functionof the queue processing section (input/output function for the controlsignal) and the function of the A-DPCH transmission power monitoringsection.

By adopting such a configuration, the mobile communication system 100can perform, within the public base station 31, a sequence of operationsfrom obtaining the transmission power of the A-DPCH through thetransmission speed control for the DSCH to the data transmission.Therefore, it is not necessary to perform transmission and reception ofthe control signal between the radio control apparatus 2 and the publicbase station 31. Accordingly, irrespective of the connection distancebetween the radio control apparatus 2 and the public base station 31,the response of the transmission speed control can be increased andmaintained.

Finally, a mobile communication program according to the embodiment ofthe present invention and a computer-readable recording medium on whichthe mobile communication program is recorded (hereinafter simplyreferred to as “recording medium”) will be described. Here, therecording medium refers to what can cause a varied state of magnetic,optical, electric or other energy corresponding to the recorded contentsof the program to occur in a reading unit provided to the hardwareresources of a general-purpose computer or the like, and communicate therecorded contents of the program to the reading unit in a form ofsignals corresponding thereto. Such recording media include, forexample, not only what is removably mounted on the computer such asmagnetic disk, optical-disk and magneto-optical disk, but also a HD(Hard Disk) fixedly mounted inside the computer, and an integrally andfirmly fixed nonvolatile semiconductor memory of firmware.

FIG. 7 is a diagram showing a configuration of a recording mediumaccording to the embodiment of the present invention. The recordingmedium 50 is provided with a program storage region 50 a that stores aprogram as shown in FIG. 7. In the program storage region 50 a, a mobilecommunication program 51 is recorded. The mobile communication program51 comprises a main module 51 a which is a program for controlling thedownward packet communication between a cell phone and a public basestation and supervises the operations, a transmission power calculationmodule 51 b that calculates the transmission power of a data signal tobe transmitted to a particular mobile communication terminal of aplurality of mobile communication terminals based on the transmissionpower of a control signal to be transmitted to the particular mobilecommunication terminal and an offset value to be applied to thetransmission power of the control signal, an upper limit storage module51 c that stores an upper limit value of the transmission power of thedata signal in storage means, a transmission power comparison module 51d that compares the calculated transmission power of the data signalwith the upper limit value stored in the storage means, and atransmission speed control module 51 e that performs control, as aresult of the comparison, for decreasing the transmission speed of thedata signal when the transmission power of the data signal is greaterthan the upper limit value, and for increasing the transmission speed ofthe data signal when the transmission power of the data signal is lessthan or equal to the upper limit value.

Preferably, the mobile communication program 51 comprises a low-speedtransmission power calculation module 51 f that calculates thetransmission power of the data signal in the case of having decreasedthe transmission speed of the data signal when the transmission power ofthe data signal is greater than the upper limit value as a result of thecomparison, and a high-speed transmission power calculation module 51 gthat calculates the transmission power of the data signal in the case ofhaving increased the transmission speed of the data signal when thetransmission power of the data signal is less than or equal to the upperlimit value as a result of the comparison.

Here, the upper limit storage module 51 c is a module that performs anoperation for storing data similar to the data stored in the memorysection 22 of the radio control apparatus 2, into storage means such asa HD or memory. The function achieved by operating each of thetransmission power calculation module 51 b, the transmission powercomparison module 51 d, the transmission speed control module 51 c, thelow-speed transmission power calculation module 51 f and the high-speedtransmission power calculation module 51 g is the same as the functionof the transmission speed control section 23 included in the radiocontrol apparatus 2.

The mobile communication program 51 may be configured such that part orall thereof is received by a communication unit of a computer fromanother equipment through a transmission medium such as a communicationline, and then recorded. To the contrary, it may be configured such thatthe mobile communication program 51 is transmitted through atransmission medium and installed in another equipment.

INDUSTRIAL APPLICABILITY

According to the present invention, the transmission speed of the datasignal transmitted in a time-division manner on a channel common to aplurality of mobile communication terminals is dynamically controlleddepending on the transmission power of the control signal transmitted ona channel specific to each of the plurality of mobile communicationterminals. That is, when the transmission power of the data signal isgreater than the upper limit value, control for decreasing thetransmission speed of the data signal is carried out. This controlallows a sufficient transmission power suitable for the transmissionspeed to be supplied to the DSCH, resulting in an increase of thecommunication quality of the data. On the other hand, when thetransmission power of the data signal is less than or equal to the upperlimit value, control for increasing the transmission speed of the datasignal is carried out. This control allows the speed of the datatransmission to be increased. As a result, a high-speed datacommunication can be achieved while suppressing the decrease ofcommunication quality.

1. A radio control apparatus for controlling downward packetcommunication between a mobile communication terminal and a base stationby using a channel specific to each of a plurality of mobilecommunication terminals to cause a control signal to be transmitted andusing a channel common to the plurality of mobile communicationterminals in a time-division manner to cause a data signal to betransmitted, comprising: calculation means for calculating, based on atransmission power of the control signal to be transmitted to aparticular mobile communication terminal of said plurality of mobilecommunication terminals and an offset value to be applied to thetransmission power of the control signal, the transmission power of thedata signal to be transmitted to said particular mobile communicationterminal; storage means for storing an upper limit value of thetransmission power of said data signal; comparison means for comparingthe transmission power of the data signal calculated by said calculationmeans with said upper limit value stored in said storage means; andcontrol means for performing control, as a result of comparison by saidcomparison means, to decrease the transmission speed of said data signalwhen the transmission power of said data signal is greater than saidupper limit value, and to increase the transmission speed of said datasignal when the transmission power of said data signal is less than saidupper limit value.
 2. The radio control apparatus according to claim 1,wherein said calculation means calculates the transmission power of saiddata signal based on an average value of the transmission powers of saidcontrol signal over a predetermined period of time and an average valueof said offset values over a predetermined period of time.
 3. The radiocontrol apparatus according to claim 1, further comprising low-speedtransmission power calculation means for calculating the transmissionpower of the data signal in the case of having decreased thetransmission speed of said data signal when the transmission power ofsaid data signal is greater than said upper limit value as a result ofcomparison by said comparison means, wherein said control means performscontrol to decrease the transmission speed of said data signal until thetransmission power of the data signal calculated by said low-speedtransmission power calculation means becomes less than or equal to saidupper limit value.
 4. The radio control apparatus according to claim 1,further comprising high-speed transmission power calculation means forcalculating the transmission power of the data signal in the case ofhaving increased the transmission speed of said data signal when thetransmission power of said data signal is less than said upper limitvalue as a result of comparison by said comparison means, wherein saidcontrol means performs control to increase the transmission speed ofsaid data signal until the transmission power of the data signalcalculated by said high-speed transmission power calculation meansreaches a maximum value within a range in which said upper limit valueis not exceeded.
 5. A mobile communication method performed by a radiocontrol apparatus for controlling downward packet communication betweena mobile communication terminal and a base station by using a channelspecific to each of a plurality of mobile communication terminals tocause a control signal to be transmitted and using a channel common tothe plurality of mobile communication terminals in a time-divisionmanner to cause a data signal to be transmitted, comprising: acalculating step of calculating, by said radio control apparatus, basedon a transmission power of the control signal to be transmitted to aparticular mobile communication terminal of said plurality of mobilecommunication terminals and an offset value to be applied to thetransmission power of the control signal, the transmission power of thedata signal to be transmitted to said particular mobile communicationterminal; a storing step of storing, by said radio control apparatus, anupper limit value of the transmission power of said data signal instorage means; a comparing step of comparing, by said radio controlapparatus, the transmission power of the data signal calculated in saidcalculating step with said upper limit value stored in said storagemeans; and a controlling step of performing control, by said radiocontrol apparatus, as a result of comparison in said comparing step, todecrease the transmission speed of said data signal when thetransmission power of said data signal is greater than said upper limitvalue, and to increase the transmission speed of said data signal whenthe transmission power of said data signal is less than said upper limitvalue.
 6. The mobile communication method according to claim 5, whereinsaid calculating step comprises calculating the transmission power ofsaid data signal based on an average value of the transmission powers ofsaid control signal over a predetermined period of time and an averagevalue of said offset values over a predetermined period of time.
 7. Themobile communication method according to claim 5, further comprising alow-speed transmission power calculating step of calculating, by saidradio control apparatus, the transmission power of the data signal inthe case of having decreased the transmission speed of said data signalwhen the transmission power of said data signal is greater than saidupper limit value as a result of comparison in said comparing step,wherein said controlling step comprises performing control to decreasethe transmission speed of said data signal until the transmission powerof the data signal calculated in said low-speed transmission powercalculating step becomes less than or equal to said upper limit value.8. The mobile communication method according to claim 5, furthercomprising a high-speed transmission power calculating step ofcalculating, by said radio control apparatus, the transmission power ofthe data signal in the case of having increased the transmission speedof said data signal when the transmission power of said data signal isless than said upper limit value as a result of comparison in saidcomparing step, wherein said controlling step comprises performingcontrol to increase the transmission speed of said data signal until thetransmission power of the data signal calculated in said high-speedtransmission power calculating step reaches a maximum value within arange in which said upper limit value is not exceeded.
 9. A mobilecommunication program for controlling downward packet communicationbetween a mobile communication terminal and a base station by using achannel specific to each of a plurality of mobile communicationterminals to cause a control signal to be transmitted and using achannel common to the plurality of mobile communication terminals in atime-division manner to cause a data signal to be transmitted,instructing a computer to perform: a calculating operation forcalculating, based on a transmission power of the control signal to betransmitted to a particular mobile communication terminal of saidplurality of mobile communication terminals and an offset value to beapplied to the transmission power of the control signal, thetransmission power of the data signal to be transmitted to saidparticular mobile communication terminal; a storing operation forstoring an upper limit value of the transmission power of said datasignal in storage means; a comparing operation for comparing thetransmission power of the data signal calculated by said calculatingoperation with said upper limit value stored in said storage means; anda controlling operation for performing control, as a result ofcomparison by said comparing operation, to decrease the transmissionspeed of said data signal when the transmission power of said datasignal is greater than said upper limit value, and to increase thetransmission speed of said data signal when the transmission power ofsaid data signal is less than said upper limit value.
 10. The mobilecommunication program according to claim 9, wherein said calculatingoperation comprises calculating the transmission power of said datasignal based on an average value of the transmission powers of saidcontrol signal over a predetermined period of time and an average valueof said offset values over a predetermined period of time.
 11. Themobile communication program according to claim 9, further instructingthe computer to perform a low-speed transmission power calculatingoperation for calculating the transmission power of the data signal inthe case of having decreased the transmission speed of said data signalwhen the transmission power of said data signal is greater than saidupper limit value as a result of comparison in said comparing operation,wherein said controlling operation instructs the computer to perform anoperation to decrease the transmission speed of said data signal untilthe transmission power of the data signal calculated by said low-speedtransmission power calculating operation becomes less than or equal tosaid upper limit value.
 12. The mobile communication program accordingto claim 9, further instructing the computer to perform a high-speedtransmission power calculating operation for calculating thetransmission power of the data signal in the case of having increasedthe transmission speed of said data signal when the transmission powerof said data signal is less than said upper limit value as a result ofcomparison in said comparing operation, wherein said controllingoperation instructs the computer to perform an operation to increase thetransmission speed of said data signal until the transmission power ofthe data signal calculated by said high-speed transmission powercalculating operation reaches a maximum value within a range in whichsaid upper limit value is not exceeded.
 13. A mobile communicationsystem comprising the radio control apparatus according to claim 1 and abase station controlled by the control means of said radio controlapparatus, the base station transmitting the data signal to said mobilecommunication terminal at the transmission speed of said data signal,wherein communication is carried out between said radio controlapparatus and said base station.